1.1 This practice covers the procedures for calculating the viscosity index of petroleum products, such as lubricating oils, and related materials from their kinematic viscosities at 40 and 100^oC.

Note 1 -- The results obtained from the calculation of VI from kinematic viscosities determined at 40 and 100^oC are virtually the same as those obtained from the former VI system using kinematic viscosities determined at 37.78 and 98.89^oC.

1.1.1 Procedure A - For petroleum products of viscosity index up to and including 100.

1.1.2 Procedure B - For petroleum products of which the viscosity index is 100 or greater.

1.2 This standard does not apply to petroleum products with kinematic viscosities less than 2.0 mm²/s (cSt) at 100^oC. Table 1 given in this practice applies to petroleum products with kinematic viscosities between 2 and 70 mm²/s (cSt) at 100^oC. Equations are provided for calculating viscosity index for petroleum products having kinematic viscosities above 70 mm²/s (cSt) at 100^oC.

Note 2 - 1 cSt = 1 mm²/s = 10⁶m²/s.

1.2.1 In cases where kinematic viscosity data are not available at temperatures of 40 and 100^oC, an estimate may be made of the viscosity index by calculating the kinematic viscosity at temperatures of 40 and 100^oC from data obtained at other temperatures. Such viscosity index data may be considered as suitable for information only and not for specification purposes. See Test Method D 341, Annex A1.

1.3 The kinematic viscosity values are determined with reference to a value of 1.0034 mm²/s (cSt) at 20.00^oC for distilled water. The determination of the kinematic viscosity of a petroleum product shall be carried out in accordance with Test Methods D 445, IP 71, ISO 3104, or ISO 2909.

1.4 The values stated in SI units are to be regarded as the standard.